Sound translating device



April 29, 1958 s. E. LEVY 2,332,845

scum) TRANSLATING DEVICE Filed April 29, 1957 2 Sheets-Sheet 1 JNVENTOR. 9Z M 5/04/67 .5 [510 Arrmwe'y April 29, 1958 s. E. LEVY 2,832,845

United Stats Patent ice 2 1,5.

sourm TRANdLATING nuvrcu Sidney E. Levy, White Plains, N. Y., assignor of one-half to Arthur Blumenfeld, New York, N. Y.

Application April 29, 1957, Serial No. 655,558

7 Claims. (Cl. 179-1155) This invention relates to loudspeakers, and more particularly to a horn driver unit having a simplified acoustic transformer or coupler utilizing a segmented annular slot.

A primary object of the invention is the provision of an improved horn type dynamic loudspeaker having a greatly expanded high frequency range, an over-all acoustic efficiency as high as 50%, and high power capacity in the high frequency range.

It is well known in the art that, to obtain high efiiciency over this range, the acoustic impedance of the air in front of the diaphragm must be matched with the mechanical impedance of the diaphragm. An impedance matching device or acoustic coupler or transformer is ordinarily used between the diaphragm and the throat of the horn. This consists basically of an extremely narrow air chamber next to the diaphragm in which the latter moves, and an arrangement or" air escapement ducts leading from this chamber to the throat of the horn. These ducts are designed to have a slight taper conforming to that of the horn, or they may be straight. There is a theoretical limit upon the maximum distance from any point on the diaphragm to the nearest duct opening, which is that it must not exceed one-quarter wave length of the highest sound wave which it is desired to reproduce efiiciently. In cases where a fairly small diaphragm is adequate for the acoustic output power desired, the ducts may have the form of annular segments. It is a second primary object of this invention to provide an acoustic coupler adapted to be economically die cast or molded in one piece complete with ducts, with no intrinsic limitations on the upper frequency range.

Another object of this invention is to provide an annular seat for the diaphragm as integral part of the acoustic coupler.

Another object is to provide means for centering the diaphragm driving coil in the magnetic air gap as an integral part of the acoustic coupler.

Other objects and features of the invention will appear when the following description is considered in connection with the annexed drawings, in which:

Fig. 1 is an end elevational view of the loudspeaker of this invention;

Fig. 2 is a partial vertical cross-sectional view of the loudspeaker of Fig. 1, the section being taken on the lines 2--2 of Fig. 1;

Fig. 3 is an enlarged detail of a section of Fig. 2 showing a portion of the diaphragm and the surrounding parts;

Fig. 4 is an end elevational View of the front of the central portion only of the acoustic coupler shown in the sectional view of Fig. 2;

Fig. 5 is an enlarged vertical cross-sectional view of the acoustic coupler as shown in Fig. 2 and taken on the line 22 of Fig. 1;

Fig. 6 is an end elevational view of the rear of the central portion only of the acoustic coupler shown in Fig. 5;

Fig. 7 is a vertical cross-sectional view of the acoustic coupler shown in Fig. 5, taken on the line 7-7.

Referring to the drawings, the speaker driver unit comprises the magnet 60, the magnetic core 61, the outer annular pole piece 66, the annular non-magnetic spacer 67, which disposes the outer pole plate at a desired annular air gap 68 (see Fig. 3) from the magnet core 61, an acoustic coupler 72, a diaphragm assembly 74, and an outer front housing 64. There is also an outer rear housing 92 and a spring washer 93, which presses against the bottom pole plate 62 and compresses the rim 79 of the diaphragm against the shelf 73 of the acoustic coupler.

Referring to Fig. 3, the diaphragm is shown as having a substantially cylindrical step portion 78 extending from the periphery of the concave side 74, and a generally fiat rim portion '79. The latter is ailixed to a shelf 73 on the acoustic coupler. Pressure of the shelf 73 on the diaphragm rim 79 is assured by relieving the diaphragm rim contacting surface at an angle 'Fll, as indicated in Fig. 5. This insures a tight acoustic seal. A resilient gasket 76 is shown in Figs. 2 and 3. it may be seen that the acoustic coupler is so contoured as to provide uniformly spaced relationship to the diaphragm inside of the edge of the shelf 73 by reason of the offset d3, which clears the rim 79, and the step ti l, which clears the step portion 78 of the diaphragm. The diaphragm assembly includes the voice coil from it aihxed to the inside surface of the cylindrical step '78 and the voice coil 77.

The acoustic coupler 72 is shown in detail in Figs. 4 to 7, inclusive. A plurality of sound-conducting channels or escapement ducts are formed between solid ridge portions 87 on a conoidal protruding portion, generally indicated at 85, of the coupler. These channels provide acoustic communication between the bowl side 80 of the coupler and the front side of the conoidal portion 85. The apertures 36 are contiguous to the channels formed between the ridges 37 on the conoidal portion 85. A duct is thereby formed to conduct sound.

It may be seen that, first, these apertures are so arranged as to provide no more than a predetermined spacing between any point in the air chamber 84a, juxtaposed to the diaphragm, such as point 96, to the edge of the nearest aperture 66; and, second, the ducts formed by the apertures and the channels are so shaped as to have a predetermined taper from the diaphragm side to the tip of the conoidal portion 35, which may be arranged to match that of the horn.

On the annular portion surrounding the bowl 810, there may be seen a shelf 73 on which the diaphragm seats. It may also be seen that the recessed annulus 83 clears the rim 79 of the diaphragm and the annular step 84 clears the cylindrical step 78 in the diaphragm and forms thereby a narrow acoustical chamber between the diaphragm and the bowl 80 of the acoustic coupler. The outer surfaces 88 of the conoidal portion are shaped to fit within a conoidal throat 89 in the front housing, which thereby constitutes the outer wall of the channels extending from the apertures 86.

The voice coil leads are brought out on opposite sides of the voice coil 77 and connected to terminals such as in a manner well known in the art. The layout of the terminal posts 95, 95' may be seen in Fig. 1. The acoustic coupler to which the posts are fastened is assembled to the outer housing by passing the assembled terminal posts through clearance holes 96 in the outer housing. There is no Way in which the polarity of the voice coil relative to the outer terminals can be accidentally reversed, since the layout avoids symmetry. This provides phasing of the leads of the voice coil so that they will be the same in every unit, relative to the outside terminal. This is necessary when connecting a plurality of loudspeakers in an array, in order to avoid sound cancellation effects.

The invention has been described as embodied in a loudspeaker, though it is to be understood that the same construction is usable as a sound pickup device.

The drawings and description are to be taken generally as illustrative rather than restrictive of the broad invention. Various changes may be made in manufacture, such as different locations of the casting parting surfaces, and the like.

In the claims the term transducer is used to indicate a sound translating device usable either as loudspeaker or microphone.

I claim:

1. In a transducer of the type described, adiaphragm with a generally curved acoustic driving portion symmetrical about a central axis, a generally flat, annular rim and a voice coil concentric therewith, a magnetic system having a concentric air gap for surrounding the voice coil, and a housing having a throat for conducting sound; a mechanical acoustic body having a conoidal front portion and a generally flat, annular portion at the base of the conoidal portion, the surface of the conoidal portion having a plurality of longitudinal tapered ridges and an equal number of channels formed therebetween, each channel having formed contiguously therewith an aperture bounded by the walls of the channel and by a portion of said generally fiat, annular portion; the rear side of said body having a central symmetrical portion curved to fit with closely spaced relationship to the acoustic driving portion of said diaphragm and defining therewith a narrow acoustic chamber; said channels cooperating with the wall of the sound conducting throat in said housing to form a plurality of sound conducting ducts having predetermined aggregate cross-sectional area relationships and communicating between closely spaced portions of the diaphragm and the end of said conoidal portion.

2. In a transducer as described in claim 1, characterized by the rear side of said body having a generally fiat, annular portion surrounding said curved portion perpendicular to the central axis of said conoidal portion to provide seating means for said diaphragm rim.

3. In a transducer as described in claim 1, characterized by centering means for the magnetic system comprising an annular offset on the rear side of said body with a cylindrical surface concentric with the axis of said conoidal portion.

4. In a transducer of the type described, a diaphragm with a generally curved, acoustic driving portion symmetrical about a central axis, a generally flat annular rim and a voice coil concentric therewith, and a magnetic system having a concentric air gap adapted for surrounding the voice coil; a mechanical acoustic body having a fluted conoidal front portion and a generally flat annular portion at the base of the conoidal portion, the surface of the conoidal portion having a plurality of longitudinal tapered ridges and an equal number of channels formed therebetween, each channel having formed contiguously therewith an aperture bounded by the walls of said channel and by a portion of said generally flat annular portion; the rear side of said body having a central symmetrical portion curved to fit with closely spaced relationship to said acoustic driving portion of said diaphragm and defining therewith a narrow acoustic chamber.

5. A mechanical acoustic body having a fluted conoidal front portion and a generally flat annular portion at the base of said conoidal portion, the surface of the conoidal portion having a plurality of longitudinal tapered ridges and an equal number of channels formed therebetween, each channel having formed contiguously .therewith an aperture bounded by the walls of the channel and by a portion of said generally flat annular portion.

6. A device as described in claim 5, characterized by the rear side of said body having a central symmetrical curved portion and a generally fiat annular portion surrounding said curved portion.

7. A device as described in claim 5, characterized by the rear side of said body having an annular portion offset from said generally fiat portion and having a cylindrical surface concentric with an axis of said curved portion.

No references cited. 

